1. Field of the Invention
This invention relates to a pressing tool for connecting pipe-shaped workpieces, having a fork-shaped receiver, a clamping tool, which is interchangeably held in this receiver by a connecting bolt and has two clamping jaws, which can be moved toward each other, and of a drive motor for operating the clamping tool. A connecting bolt can be pushed through bores in the fork-shaped receiver and in the clamping tool for interchangeably maintaining the clamping tool in the fork-shaped receiver.
2. Description of Prior Art
Pressing tools are known, which have pipe-shaped workpieces that are pressed together and two elements that are connected with each other in this way. Known cylinder-shaped workpieces are, for example, press sleeves, press fittings or connecting sleeves, as well as pipe sections, which can be pushed into each other and pressed together. These pressing tools are mostly constructed in a pistol shape and have a clamping tool. The clamping tool encloses a workpiece to be pressed. When the pressing tool is activated, the clamping jaws of the clamping tool are pressed together. So that various diameters of workpieces, such as coupling elements, can be processed by the same pressing tool if designed in such a way that appropriately dimensioned clamping tools can be simply exchanged.
The pressing tool has a fork-shaped receiver, in which the clamping tool is interchangeably held by a connecting bolt. The fork-shaped receiver and the clamping tool have bores for this purpose, through which passes the connecting bolt.
However, such pressing tools are tools with an increased accident risk. Several work accidents have already occurred, wherein the clamping tool was ejected in an uncontrolled manner and the fork-shaped receiver was bent open and deformed. Moreover, these pressing tools preform an increased number of incorrect pressings. Damages occur with both electro-mechanically and electro-hydraulically operated pressing tools.
In accordance with European Patent Reference EP-A-0 712 696, a monitoring element monitors the connecting bolt in its completely pushed-in position and is connected with the drive motor via a switch element.
Even if the clamping tool is correctly held in the pressing tool, this alone does not assure precise pressing of the pipe-shaped workpieces. The reasons for qualitatively unsatisfactory pressings can be of a wide variety. Besides functional reasons of the pressing tool, there are reasons which are connected with unsatisfactory processing. For example, the tool, or respectively the clamping jaws, can be dirty, so that sufficient closing of the clamping tool cannot be achieved, or the size of the pipe connector or pressing sleeve does not correspond to the size for which the corresponding tool is provided.
For these reasons a pressing tool was proposed in accordance with European Patent Reference EP-A-0 858 850, in which the length of the stroke of the drive which acts on the clamping tool is monitored. The appropriate length of the stroke for completely closing the clamping tool is known. This length of the stroke can also be indirectly determined, for example by a volumetric measurement of the hydraulic fluid in the case where the pressing tool is hydraulically operated. However, to monitor correctly, the pressing tool must determine which clamping tool is in use. Such a clamping tool determination requires an electronic data exchange between the clamping tool and the pressing tool, as well as appropriate electronic logic means, by which the information can be evaluated for appropriate signals that indicate a correct or an incorrect pressing operation. Such electronic monitoring devices then can be combined without problems with further electronic information, which also indicates the correct operation and the perfect state of the pressing tool.
Since these pressing tools are often employed at building sites, soiling, in particular of the clamping tool, can hardly be avoided. Such soiling then often leads to interruptions in the electronic transmission, and therefore to erroneous information.
A pressing tool is also described in German Patent Reference DE-A-19 631 019 wherein the final press position of the clamping jaws is monitored. Accordingly, the clamping tool can detect this final press position and pass it on to a display device. One problem with transmitting information from the clamping tool to the pressing tool remains. Appropriate electronics must be integrated into the clamping jaws in addition to elements which are also mechanically intricate. Here, the functional ability of the checking means is often hard to determine, and the user can also not see whether their functioning is still assured. Accordingly, the device continuously provides the information that the pressing process is unsatisfactory, while in actuality the pressing process is satisfactory, but there is an error in monitoring.